title: Voltage sensor interaction site for selective small molecule inhibitors of voltage-gated sodium channels.
abstract: Voltage-gated sodium (Nav) channels play a fundamental role in the generation and propagation of electrical impulses in excitable cells. Here we describe two unique structurally related nanomolar potent small molecule Nav channel inhibitors that exhibit up to 1,000-fold selectivity for human Nav1.3/Nav1.1 (ICA-121431, IC50, 19 nM) or Nav1.7 (PF-04856264, IC50, 28 nM) vs. other TTX-sensitive or resistant (i.e., Nav1.5) sodium channels. Using both chimeras and single point mutations, we demonstrate that this unique class of sodium channel inhibitor interacts with the S1-S4 voltage sensor segment of homologous Domain 4. Amino acid residues in the "extracellular" facing regions of the S2 and S3 transmembrane segments of Nav1.3 and Nav1.7 seem to be major determinants of Nav subtype selectivity and to confer differences in species sensitivity to these inhibitors. The unique interaction region on the Domain 4 voltage sensor segment is distinct from the structural domains forming the channel pore, as well as previously characterized interaction sites for other small molecule inhibitors, including local anesthetics and TTX. However, this interaction region does include at least one amino acid residue [E1559 (Nav1.3)/D1586 (Nav1.7)] that is important for Site 3 α-scorpion and anemone polypeptide toxin modulators of Nav channel inactivation. The present study provides a potential framework for identifying subtype selective small molecule sodium channel inhibitors targeting interaction sites away from the pore region.
authors.affiliation: Icagen Inc currently Neusentis, Research Unit of Pfizer Inc, Durham, NC 27703, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: McCormack
authors.forename: Sonia
authors.initials: S
authors.lastname: Santos
authors.forename: Mark L
authors.initials: ML
authors.lastname: Chapman
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Krafte
authors.forename: Brian E
authors.initials: BE
authors.lastname: Marron
authors.forename: Christopher W
authors.initials: CW
authors.lastname: West
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Krambis
authors.forename: Brett M
authors.initials: BM
authors.lastname: Antonio
authors.forename: Shannon G
authors.initials: SG
authors.lastname: Zellmer
authors.forename: David
authors.initials: D
authors.lastname: Printzenhoff
authors.forename: Karen M
authors.initials: KM
authors.lastname: Padilla
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Lin
authors.forename: P Kay
authors.initials: PK
authors.lastname: Wagoner
authors.forename: Nigel A
authors.initials: NA
authors.lastname: Swain
authors.forename: Paul A
authors.initials: PA
authors.lastname: Stupple
authors.forename: Marcel
authors.initials: M
authors.lastname: de Groot
authors.forename: Richard P
authors.initials: RP
authors.lastname: Butt
authors.forename: Neil A
authors.initials: NA
authors.lastname: Castle
mesh_terms: D000081:Acetamides / Q000494:pharmacology*; D020816:Amino Acid Motifs / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D055724:Electrophysiological Phenomena / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D062552:NAV1.3 Voltage-Gated Sodium Channel / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D016415:Sequence Alignment; D013844:Thiazoles / Q000494:pharmacology*; D061567:Voltage-Gated Sodium Channel Blockers / Q000494:pharmacology*
chemical_list: D000081:Acetamides; C583593:ICA-121431; D062552:NAV1.3 Voltage-Gated Sodium Channel; D013844:Thiazoles; D061567:Voltage-Gated Sodium Channel Blockers